Patients with osteopenia or osteoporosis may avoid complications of orthognathic surgery if clinicians screen for low bone density at osteotomy sites by measuring Hounsfield unit (HU) values on computed-tomographic (CT) scans before surgery. The research was published online August 19 in The Journal of Craniofacial Surgery.

The finding is among those discovered by scientists in South Korea who aimed to investigate the validity of HU measurements in evaluating bone density at sites in the mandible and maxilla in patients who had CT scans and were divided into 2 groups—abnormal (with osteopenia or osteoporosis) and normal. The criterion standard test for evaluating bone density is dual-energy X-ray absorptiometry (DEXA), but it is difficult to perform in the mandible and maxilla. Previous research shows that HU measurement on CT scans is useful for the evaluation of bone density of the mandible and maxilla. However, to the authors’ knowledge no previous research was conducted on the correlation between orthognathic surgery and osteoporosis.

The scientists also aimed to evaluate the difference in bone density of osteotomy sites in both groups, the effect of osteopenia and osteoporosis in both groups, and to clarify the effect of osteopenia and osteoporosis on bone density of the maxillofacial region overall.

To measure, compare, and evaluate HU values of CT scans, scientists reviewed the charts of 80 patients who had undergone both lumbar DEXA and facial CT from November 2003 through July 2014 at the Department of Dentistry in the School of Medicine at Ajou University in Suwon, South Korea. Patients who had T-scores on DEXA at L1 through L3 of less than 1 were assigned to the abnormal group (40 patients) and those with T-scores of –1 or higher at those sites were to the normal group (40 patients).

CT scans were obtained with a 64-section multidetector CT scanner. HU values were measured 3 times by each of 2 clinicians. The bilateral mean measurement was selected as the representative value. Scientists investigated differences between the normal and abnormal groups and sought correlations between T-scores and HU values by focusing on 7 osteotomy sites in which specific orthognathic surgery techniques were applied.

Evaluating 1,120 regions of interest, scientists found significant differences in mean HU values between the normal group and the abnormal group at all 7 of the maxillary and mandibular sites investigated, with HU values being significantly higher in the normal group. They found positive correlations between T-scores on DEXA and HU values on CT scans at all of the osteotomy sites, and all of the correlations were statistically significant.

In the discussion, the authors said their findings indicated that HU value might reflect bone density to some degree. “Therefore, in our view, CT could be a useful tool for identifying patients with decreased bone density,” they said. “In particular, because the HU values in the maxillary and mandibular osteotomy sites were lower in the group with osteopenia or osteoporosis than in the normal group, it was considered that the risk of a bad split or unfavorable fracture during osteotomy would be greater in these patients owing to the lower bone density.”

The authors also suggested as a result of their research that osteoporosis could be an independent factor in accidental fracture and have effects on the alveolar bone and both the mandible and maxilla. They pointed out that although bone density in patients with osteoporosis may be lower than in those that do not, it is recognized that a diagnosis of osteoporosis or osteopenia does not increase the risk of implant failure.

They said their study demonstrates the need to exercise caution during orthognathic surgery in patients with osteoporosis or osteopenia and called for more studies on such correlations.

Craniomaxillofacial injuries showed an association with cervical spine injuries (CSIs), with midfacial trauma and upper CSI being the most common combination of conditions encountered by surgeons, scientists reported.
Because the underestimation of recognizing or failure to recognize these collective injuries can have devastating results and are associated with significant mortality, the findings are important. “When maxillofacial surgeons are involved in the initial assessment of these cases, it is essential that they are aware of the possibility of cervical spine injury and initiate additional diagnostics,” scientists in Germany who conducted the 10-year study advised. They analyzed incidence of patients with primary maxillofacial trauma who also sought treatment for significant CSIs, and they published their study in the September issue of Journal of Cranio-Maxillo-Facial Surgery.

They reviewed the charts of 3,956 patients at a trauma center who experienced craniomaxillofacial injuries and CSIs and identified 50 charts that met the inclusion criteria. In addition, they conducted a literature search in PubMed using the search terms “maxillofacial” AND “cervical spine” AND “injury.” The literature search yielded 12 international articles that met the inclusion criteria.

Scientists found that among all craniomaxillofacial injuries, 1.3% showed an association with CSIs and that, overall, CSIs are prevalent in 0.8% to 11% of patients with maxillofacial trauma.

“As maxillofacial surgeons are regularly involved in the initial assessment of trauma patients, it is essential that they are aware of the possibility of cervical spine injury,” the authors said in their discussion of blunt CSI.

“Because maxillofacial surgeons are not typically involved in cervical spine pathologies in cases of apparently isolated maxillofacial trauma, there may be a risk of underestimating an occult blunt cervical spine injury,” they also said. “Familiarity with the appropriate diagnostic algorithm is therefore generally required in all involved disciplines who treat head and neck injuries.”

The article includes sections on risk factors and diagnostic imaging in CSIs, the biomechanics of the cervical spinal column, and factors other than the mechanisms of injury that require clinical understanding, as well as therapies.

“Increased complexity of craniofacial trauma and difficult airways escalate the individual risk of potential neurologic complications resulting from concomitant cervical spine injury, and appropriate imaging can be performed following intubation,” the authors said in the conclusions. They also found a risk of experiencing concomitant CSI more prominently in elderly patients with isolated maxillofacial injuries and that craniofacial injuries complicated by CSIs were associated with significant mortality (8%).

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Computed tomography and early changes in patients treated with bisphosphonates

It is well recognized that bisphosphonates (BP) are implicated in the development of medication-related osteonecrosis of the jaw (MRONJ). Although the incidence is relatively low, early detection and the ability to predict the areas in which MRONJ might arise is important for effectively managing the care of patients with MRONJ.

Interested in early changes detectable by computed tomography (CT) in the mandible of patients treated with BP, scientists in Japan conducted a retrospective study comparing the CT features of mandibular cancellous and cortical bones between patients who received BP and those who did not. The study group consisted of 24 patients (5 males and 19 females) from 1 dental hospital who had received BP therapy and had developed MRONJ from January 2008 through August 2015. Eight patients had undergone intravenous BP administration, and 16 patients had undergone oral administration. A MRONJ diagnosis was made according to the position papers of the American Association of Oral and Maxillofacial Surgeons.

For comparison, scientists also enrolled 20 patients who had experienced osteomyelitis and 20 patients who did not have disease in the jaw and had never received BP treatment. Scientists measured the values of cancellous and cortical bone and cortical bone widths in all groups and affected and unaffected areas of disease.

However, before taking measurements, scientists confirmed the relationship between bone mineral density and CT values in the pre-examination and confirmed a correlation between CT and bone mineral density values. They conducted comparisons of the CT values for all groups on the basis of these relationships.

Among primary results, scientists found that CT values of cancellous bone in patients treated with BP increased, even in unaffected areas or in the early stage of MRONJ that did not involve exposed bone. In the discussion, the authors said this might reflect bone sclerosis induced by chronic inflammation and subsequent circulatory disturbance. “These results suggest that cancellous bone in BP-treated patients becomes sclerotic, although longitudinal studies are needed to confirm this,” they said.

In light of their findings, they concluded that cancellous bone CT values appear to be a possible index to assess the early changes of the mandible in patients treated with BP.

In the discussion, the authors noted that their study showed no significant difference in bone densities and cortical bone widths based on administration route (intravenous versus oral) or treatment duration (≥ 3 years versus ˂ 3 years). They ventured that it may be of value to assess bone density of the jaw in asymptomatic patients treated with BP, as CT values may lead to identification of early changes of the jaw in patients treated with BP and provide clues regarding bone change.

The study was published in the September issue of Oral Surgery Oral Medicine Oral Pathology and Oral Radiology.

Research published online September 13 in Oral and Maxillofacial Surgery identified preoperative risk factors associated with postoperative oroantral perforation. The study’s authors advised clinicians to consider these risk factors before performing surgery to remove the maxillary third molar.

Oroantral perforation is a common complication that occurs with the removal of the maxillary third molar, and it is well known that it is associated with the tooth’s proximity to the maxillary sinus floor. Although panoramic radiography is frequently used by oral surgeons to visualize the third molar and determine the risk of oroantral perforation, the relationship between the radiographic findings and oroantral perforation is controversial, and clinicians are therefore unable to precisely inform patients of the risk. In fact, scientists conducting the study found few previous studies that quantitatively analyzed contributing risk factors and none that evaluated the multivariate relationships between them.

To investigate these relationships, the scientists conducted a retrospective study of 741 teeth from patients (315 male and 426 female) who had surgical extraction of maxillary third molars at the Graduate School of Medicine at Kobe University in Kobe, Japan, and Kakogawa East City Hospital in Kakogawa, Japan, from April 2009 through March 2013. In these cases, oroantral perforation was identified by the creation of oral bubbles following a pressure test (nose blowing), careful probing of the extraction socket using a blunt sinus probe, and audible changes to the nature of the noise produced by vacuum suction across the socket. Panoramic radiographs were obtained for all patients, and the predictive variables of preoperative panoramic findings were determined by the authors who then analyzed the association of each variable with oroantral perforation.

Among the results, scientists found that overall incidence of oroantral perforation was 3.1% (its prevalence was significantly higher in patients with periocoronitis or sinusitis than in those with caries, which scientists deemed logical as most caries occurs in erupted or partially impacted teeth, whereas fully impacted teeth are much closer in proximity to the sinus floor).

Scientists said the lower incidence in this study compared with the findings of other studies cited (13% and 5%, respectively), may be due to the Japanese patient sample, as tooth root length in most Japanese patients is shorter than that of white patients.

Scientists found the performance of an incision, a mesioangular angulation, and a type 3 root-sinus classification to be highly significant risk factors for oroantral perforation.

In the discussion, they said that a 2-dimensional image may produce misleading data regarding the actual proximity of the maxillary third molar to the sinus floor and should be supported by obtaining additional computed tomographic scans to clarify the 3-dimensional relationship between the 2 structures. They predicted the validity of such an approach would be investigated in future studies.

“The preoperative identification of risk factors associated with postoperative oroantral perforation would enhance the treatment outcome in patients,” the authors said in conclusion. “Clinicians should give additional consideration to these risk factors prior to performing surgical operations to remove the maxillary third molar.”

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What is Specialty Scan?

This is one in a series of quarterly newsletters updating dentists on selected specialties in dentistry. Information presented is aggregated and summarized from previously published materials, each item attributed to its publication of origin. This issue of JADA Specialty Scan focuses on oral and maxillofacial radiology, the fourth in the series on this topic for 2016. Other Specialty Scan issues are devoted to endodontics, oral pathology, orthodontics, periodontics and prosthodontics. The ADA has engaged the specialty organizations in these areas as well as its own Science Institute and Division of Legal Affairs to assist with these newsletters. We welcome feedback on this and all Specialty Scan issues.

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